Antisocial Personality Disorder is a virulent adult disorder that clearly has its origins in childhood conduct problems. There are critical gaps in our knowledge of the development of Antisocial Personality, however, that will be addressed by the proposed study. Although most previous studies suggest that all adults with Antisocial Personality met criteria for Conduct Disorder (CD) in childhood, some theorists posit that many adults with Antisocial Personality did not exhibit CD during childhood, but met criteria for Attention-Deficit Hyperactivity Disorder (ADHD) instead. We will address this important controversy by testing the hypothesis that CD always precedes Antisocial Personality developmentally. A corollary to our hypothesis is that boys with ADHD are, in fact, at increased risk for Antisocial Personality, but only if they exhibit comorbid oppositional defiant disorder (ODD) that leads to CD (usually prior to adolescence). The most important gap in current knowledge, however, stems from evidence suggesting that fewer than half of youths with CD eventually develop Antisocial Personality. There is a need to develop an adequate theory of the etiology of Antisocial Personality, so that we can distinguish between CD that is limited to childhood and adolescence and CD that is a stage in the development of Antisocial Personality. Once such knowledge is available, it will be possible to study Antisocial Personality at the time of its origination during childhood (and intervene at that time to prevent its development). For this purpose, we propose to continue a prospective study of clinic- referred boys begun eight years ago, and follow them into early adulthood to test our hypotheses about the development of Antisocial Personality. This prospective study will be the first to use data collected annually during childhood on CD and a wide range of relevant variables to determine the characteristics of youths with CD who go on to develop Antisocial Personality. In secondary analyses, we will also examine a broad range of developmental outcomes of children with disruptive behavior disorders who do not develop Antisocial Personality.